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@@ -158,6 +158,48 @@ Everything is in place treated specially. * Synchronize fat files with `git fat push` and `git fat pull`. +## Retroactive import using `git filter-branch` [Experimental] + +Sometimes large objects were added to a repository by accident or for +lack of a better place to put them. _If_ you are willing to rewrite +history, forcing everyone to reclone, you can retroactively manage those +files with `git fat`. Be sure that you understand the consequences of +`git filter-branch` before attempting this. This feature is experimental +and irreversible, so be doubly careful with backups. + +### Step 1: Locate the fat files + +Run `git fat find THRESH_BYTES > fat-files` and inspect `fat-files` in +an editor. Lines will be sorted by the maximum object size that has been +at each path, and look like + + something.big filter=fat -text # 8154677 1 + +where the first number after the `#` is the number of bytes and the +second number is the number of modifications that path has seen. You +will normally filter out some of these paths using grep and/or an +editor. When satisfied, remove the ends of the lines (including the `#`) +and append to `.gitattributes`. It's best to `git checkout .` and commit +at this time (likely enrolling some extant files into `git fat`). + +### Step 2: `filter-branch` + +Copy `.gitattributes` to `/tmp/fat-filter-files` and edit to remove +everything after the file name (e.g., `sed s/ \+filter=fat.*$//`). +Currently, this may only contain exact paths relative to the root of the +repository. Finally, run + + git filter-branch --index-filter \ + 'git fat index-filter /tmp/fat-filter-files` \ + --tag-name-filter cat -- --all + +When this finishes, inspect to see if everything is in order and follow +the +[Checklist for Shrinking a Repository](http://www.kernel.org/pub/software/scm/git/docs/git-filter-branch.html#_checklist_for_shrinking_a_repository) +in the `git filter-branch` man page, typically `git clone +file:///path/to/repo`. Be sure to `git fat push` from the original +repository. + ## Implementation notes The actual binary files are stored in `.git/fat/objects`, leaving `.git/objects` nice and small. |